Infrared camera filter wheel systems and methods

ABSTRACT

Various techniques are provided for identifying filters used with infrared cameras. A plurality of filters may be installed in a filter wheel of an infrared camera. Identifiers associated with the filters may be read by the infrared camera to identify the various types of filters currently installed in the filter wheel. The installed filters can be selected by the camera or a user for use in particular applications as desired. For example, filters may be selected based on associations between the filters, filter identifiers, and targets stored in a table or other record maintained by the infrared camera. Settings of the infrared camera may be adjusted in response to filter selections.

BACKGROUND

1. Field of the Invention

The present invention relates generally to infrared cameras and, moreparticularly, to techniques for filtering infrared wavelengths providedto infrared cameras.

2. Related Art

As is well known, infrared cameras can be used to capture infraredimages of desired targets. In this regard, different targets may radiateand/or absorb various infrared wavelengths depending, for example, ontheir material composition and properties. Thus, in order to captureimages of particular targets, it is often necessary to filter theinfrared wavelengths received by an infrared camera's sensor circuitry.

Unfortunately, conventional filtering techniques typically require auser to select filters that are suitable for particular applications.After a user has identified an appropriate filter, the user manuallyattaches the filter to an infrared camera which then captures aninfrared image of a target. If a user wishes to view another target, adifferent filter may be needed. In this case, the user must remove thepreviously-installed filter, identify a new appropriate filter, andattach the new filter to the infrared camera before capturing anotherinfrared image.

The above approach can be cumbersome for users, especially if images ofdifferent types of targets must be repeatedly captured. Moreover, userswith limited knowledge of the infrared wavelengths or filters associatedwith particular targets may be unable to successfully select the filtersnecessary to capture desired images. Accordingly, there is a need for animproved approach to the selection of filters used with infrared camerasthat overcomes some or all of the deficiencies discussed above.

SUMMARY

Various techniques are provided for identifying filters used withinfrared cameras. For example, a plurality of filters may be installedin a filter wheel of an infrared camera. Identifiers associated with thefilters may be read by the infrared camera to identify the various typesof filters currently installed in the filter wheel. The installedfilters can be selected by the camera or a user for use in particularapplications as desired. Filters may be selected based on associationsbetween the filters, filter identifiers, and targets stored in a tableor other record maintained by the infrared camera. In addition, settingsof the infrared camera may be adjusted in response to filter selections.

In one embodiment, an infrared camera includes an infrared sensor; afilter wheel comprising: a plurality of filters adapted to selectivelyfilter infrared radiation prior to the infrared radiation being receivedby the infrared sensor, and a plurality of filter identifiers associatedwith the filters, wherein each filter identifier identifies acorresponding one of the filters; a plurality of sensors adapted to readthe filter identifiers to identify the filters installed in the filterwheel; a memory; and a processor adapted to store in the memory a recordof the filters installed in the filter wheel based on the filteridentifiers read by the sensors.

In another embodiment, a filter wheel includes a plurality of filtersadapted to selectively filter infrared radiation corresponding to aplurality of targets; and a plurality of filter identifiers associatedwith the filters, wherein each filter identifier identifies acorresponding one of the filters, wherein the filter identifiers areadapted to be read by sensors of an infrared camera.

In another embodiment, a method of identifying filters of an infraredcamera includes scanning a plurality of filter identifiers associatedwith the filters installed in a filter wheel of the infrared camera,wherein the filters are adapted to selectively filter infrared radiationprior to the infrared radiation being received by an infrared sensor ofthe infrared camera; determining whether a selected filter is installedin the filter wheel based on the scanning; and rotating the filter wheelto position the selected filter in front of an infrared sensor of theinfrared camera if the selected filter is installed in the filter wheel.

In another embodiment, an infrared camera includes a plurality offilters adapted to selectively filter infrared radiation prior to theinfrared radiation being received by an infrared sensor for the infraredcamera; means for securing the filters; means for identifying each ofthe filters; means for reading the identifying means to identify thefilters installed in the securing means; and means for storing a recordof the filters installed in the securing means based on the identifyingmeans read by the reading means.

The scope of the invention is defined by the claims, which areincorporated into this section by reference. A more completeunderstanding of embodiments of the present invention will be affordedto those skilled in the art, as well as a realization of additionaladvantages thereof, by a consideration of the following detaileddescription of one or more embodiments. Reference will be made to theappended sheets of drawings that will first be described briefly.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an exploded view of an infrared camera in accordancewith an embodiment of the invention.

FIG. 2 illustrates a front side view of a filter wheel in accordancewith an embodiment of the invention.

FIG. 3 illustrates a back side view of a filter wheel in accordance withan embodiment of the invention.

FIG. 4 illustrates an exploded view of a filter wheel in accordance withan embodiment of the invention.

FIG. 5 illustrates a filter holder in accordance with an embodiment ofthe invention.

FIG. 6 illustrates a filter in accordance with an embodiment of theinvention.

FIG. 7 illustrates a filter identifier in accordance with an embodimentof the invention.

FIG. 8 illustrates a plurality of filter identifiers in accordance withan embodiment of the invention.

FIG. 9 illustrates a front view of an infrared camera in accordance withan embodiment of the invention.

FIG. 10 illustrates a block diagram of an infrared camera in accordancewith an embodiment of the invention.

FIG. 11 illustrates a process of using a filter wheel in accordance withan embodiment of the invention.

FIG. 12 illustrates a process of scanning a plurality of filteridentifiers in accordance with an embodiment of the invention.

FIG. 13 illustrates a rear view of an infrared camera in accordance withan embodiment of the invention.

Embodiments of the present invention and their advantages are bestunderstood by referring to the detailed description that follows. Itshould be appreciated that like reference numerals are used to identifylike elements illustrated in one or more of the figures.

DETAILED DESCRIPTION

FIG. 1 illustrates an exploded view of an infrared camera 100 inaccordance with an embodiment of the invention. Infrared camera 100includes a main body 110 to which various covers may be attached such asa front cover 102, a back cover 104, a top cover 106, and a bottom cover108 using screws 190 or other appropriate fasteners. Infrared camera 100also includes a lens 160 shown in FIG. 1 attached to front cover 102.

Main body 110 includes a shutter 116 which may be selectively positionedin front of an aperture 112 by an appropriate servo motor. Shutter 116may also operate as a calibration flag to facilitate calibration ofsensor circuitry of infrared camera 100. Main body 110 may furtherinclude an infrared sensor and associated circuitry further describedherein.

A filter wheel 120 is attached to main body 110. Filter wheel 120 may berotated to selectively position various filters in front of aperture 112to filter infrared wavelengths received through lens 160.

Back cover 104 includes a communication link 170 (e.g., a gigabitethernet link, a gigabit serial image data output, a GigE Vision®interface, or other communication link) which may interface withappropriate circuitry of main body 110 for data communication (forexample, passing infrared image data). Additional circuitry 180 isattached to back cover 104 which may be used to provide, for example,various connections and/or a display which may be viewed by a user fromthe opposite side of back cover 104 as further described herein.

FIGS. 2-8 illustrate further aspects of filter wheel 120 and relatedcomponents. Filter wheel 120 may be used to hold or otherwise secure aplurality of filters 140. As shown, filter wheel 120 includes a ring 128and a plate 126 configured to receive a plurality of filter holders 130.Filter wheel 120 also includes a shaft 129 which may be mechanicallyengaged with a filter wheel gear 122. Filter wheel 120 further includesa plurality of position identifiers 134 which may be read by appropriatesensors of infrared camera 100 to align filter wheel 120.

Filter holders 130 may be opened as shown in FIG. 5 to receive opticalfilters 140 which are secured in filter wheel 120 by filter holders 130.In this regard, users of infrared camera 100 may selectively install andremove various filters 140 from filter holders 130 as may be desired forparticular applications. Although four filter holders 130 and fourfilters 140 are shown in embodiments illustrated in FIGS. 2-4, anydesired number filter holders 130 and filters 140 may be used in otherembodiments, as discussed further herein.

FIG. 6 illustrates an example of one of filters 140. As shown in FIG. 6,filter 140 includes filtering material 144 surrounded by an outer ring142. When installed in filter wheel 120, outer ring 142 is clamped byone of filter holders 130 which leaves substantially all of filteringmaterial 144 (e.g., conventional filtering materials) exposed. Filter140 may also include markings 146 such as colored dots or other markingsto distinguish filter 140 when it is not installed in one of filterholders 130.

In one embodiment, filter 130 may have a thickness of approximately 1mm, outer ring 142 may have an outside diameter of approximately 25.4mm+/−0.2 mm, and filtering material 144 may have a diameter ofapproximately 24 mm or greater. Filters 140 having other dimensions maybe used in other embodiments.

Different filters 140 may be used to filter various ranges of infraredwavelengths. For example, the following Table 1 identifies filteringcharacteristics of several different filters 140 available fromSpectrogon US, Inc. of Parsippany, N.J. which may be used in variousembodiments:

TABLE 1 Filter BP BP BP Identifier Center Width Low BP High BlockingSpectrogon 150 Filter Name/Target Type (nm) (nm) (nm) (nm) (nm) Part No.1 ND 1.0 ND — — 2000 5000 — ND-IR-OD-1.0-025.4 × 1.0 mm 2 ND 2.0 ND — —2000 5000 — ND-IR-OD-2.0-025.4 × 1.0 mm 3 ND 3.0 ND — — 2000 5000 —ND-IR-OD-3.0-025.4 × 1.0 mm 4 ND 0.3 ND — — 2000 5000 —ND-IR-OD-0.3-025.4 × 1.0 mm 5 ND 0.6 ND — — 2000 5000 —ND-IR-OD-0.6-025.4 × 1.0 mm 6 ND 1.45 ND — — 2000 5000 —ND-IR-OD-1.45-025.4 × 1.0 mm 7 Standard MWIR BBP — — 3000 5000 —BBP-3000-5000c 8 ATM BBP — — 3400 4170 — BBP-3400-4170c 9 Solar Block(SRX) LP — — 3500 5000  100 LP-3500 10 Thru Glass (TGL) BP 2345 100 22952395 3500 BP-2345-100 11 Glass High Temp BP 5000 145 4928 5073 —BP-5000-145 (GHT) 12 Narrow Band Flame BP 3900 150 3825 3975 —BP-3900-150 or HT 13 Broad Band Flame BBP — — 3700 4200 — BBP-3750-4020c14 Polyethylene (PEN) BP 3450 100 3400 3500 — BP-3450-100 15 Plastic BP3410 130 3345 3475 — BP-3410-130 16 CO2 BP 4350 180 4260 4440 —BP-4275-200 17 Nitrous-Oxide BP 4500 160 4420 4580 — BP-4500-160 18 COSNP 4220  85 4178 4263 — NB-4220-085

As shown in Table 1, various types of filters 140 may be used such asneutral density (ND) filters, broad-bandpass (BBP) filters,longwave-pass (LP) filters, bandpass (BP) filters, and shortwave-pass(SP) filters. Filters 140 may filter infrared wavelength ranges suitablefor infrared images of different targets. For example, the “CO2” filter140 passes infrared wavelengths suitable for capturing infrared imagesof carbon dioxide gas.

Each filter 140 is associated with a corresponding filter identifier 150which may be read by infrared camera 100 to identify each filter 140. Inone embodiment, filter identifiers 150 may be implemented as labelsattached to filter holders 130 associated with various filters. Inanother embodiment, filter identifiers 150 may be etched, painted, orotherwise marked on filter holders 130. In other embodiments, filteridentifiers 150 may be provided on filters 140, other portions of filterwheel 120, and/or other portions of infrared camera 100 whereappropriate.

FIG. 7 illustrates an embodiment of one of filter identifiers 150implemented as a label encoded with a six bit binary number. As shown inFIG. 7, filter identifier 150 includes six regions 152A-F, each of whichcorresponds to one bit of a six bit binary number, with region 152Acorresponding to the least significant bit position. In this embodiment,regions 152A-F are separated by lines 156. In another embodiment, lines156 may be omitted.

In FIG. 7, dark (e.g., non-reflective) surfaces in regions 152A, 152C,and 152D correspond to binary values of 1, and light (e.g., reflectiveor mirrored) surfaces in regions 152B, 152E, and 152F correspond tobinary values of 0. Accordingly, in this embodiment, filter identifier150 of FIG. 7 corresponds to the binary value: 001101. As identified inregion 154, this filter identifier 150 also corresponds to the decimalvalue: 13. Thus, it will be appreciated that filter identifier 150 ofFIG. 7 identifies the “Broad Band Flame” filter 140 of Table 1. FIG. 8illustrates additional examples of filter identifiers 150 having binaryvalues ranging from 00000 to 010111 (0 to 23 in decimal values).

It will be appreciated that by encoding filter identifiers 150 using sixbit binary numbers, up to 64 unique filter identifiers 150 may beprovided. However, any desired number of binary numbers or otherencoding methods may be used in other embodiments.

FIG. 3 illustrates several additional examples of filter identifiers 150implemented as labels attached to filter holders 130. As shown in FIG.3, filter identifiers 150 are visible from the back side of filter wheel120 while filters 140 and filter holders 130 are installed in filterwheel 120. Advantageously, this permits filter identifiers 150 to beread by infrared camera 100 while filter wheel 120 is installed ininfrared camera 100.

As shown in FIG. 2, each of filter holders 130 includes a label 132which may be viewed from a front side of filter wheel 120. Label 132provides a reminder to a user of filter wheel 120 to rescan filters 140installed in filter wheel 120 after filters 140 have been replaced. Inanother embodiment, infrared camera 100 may remind the user to rescanfilters 140 after filters 140 have been replaced, or may perform anautomated rescan as further discussed herein.

FIG. 9 illustrates a front side view of main body 110 of infrared camera100 in accordance with an embodiment of the invention. In FIG. 9, filterwheel 120 and shutter 116 have been removed from main body 110 toillustrate various components positioned behind filter wheel 120. Thesecomponents include a plurality of filter identifier sensors 114, afilter wheel alignment sensor 116, a filter wheel gear 122, and a drivegear 124.

When installed on main body 110, filter wheel 120 may be mechanicallyengaged with filter wheel gear 122 which is mechanically engaged withdrive gear 124. Drive gear 124 may be operated, for example, by astepper motor housed within main body 110. Thus, as drive gear 124rotates in response to the stepper motor, filter wheel gear 122 alsorotates which causes filter wheel 120 to rotate due to theabove-described mechanical engagement.

Filter identifier sensors 114 may be used to read filter identifiers 150associated with various filters of filter wheel 120 to identify thevarious types of filters currently installed in filter wheel 120. Filterwheel alignment sensor 116 may be used to read position identifiers 134(e.g., implemented by reflective or mirrored surfaces) on filter wheel120 to determine when filter wheel 120 has been rotated to variouspositions. Filter identifier sensors 114 and filter wheel alignmentsensor 116 may be implemented, for example, as optical sensorsconfigured to detect reflections from particular regions 152A-F offilter identifiers 150 and from position identifiers 134. In otherembodiments, filter identifier sensors 114 and filter wheel alignmentsensor 116 may be implemented as mechanical sensors, electro-mechanicalsensors, or other types of sensors appropriate to various applications.

FIG. 10 illustrates a block diagram of infrared camera 100 in accordancewith an embodiment of the invention. Infrared camera 100 includes aprocessor board 1020 which controls the operation of the variouscomponents of infrared camera 100. For example, in one embodiment,processor board 1020 may control the various components illustrated inFIG. 10. Processor board 1020 includes a processor 1022 (e.g., amicrocontroller, microprocessor, logic circuit, programmable logicdevice, or other appropriate processing device), a memory 1024, andother appropriate control circuitry. Infrared camera 100 also includes apower board 1030 that is connected to a power supply 1034 (e.g.,batteries or an external power supply) through a power switch 1032 anddistributes electrical power to the various components of infraredcamera 100 as shown in FIG. 10.

An infrared sensor (e.g., a focal plane array (FPA) or otherconventional infrared detector) 1014 is configured to detect infraredimages corresponding to infrared radiation 1050 received through filterwheel 120. The detected infrared images are passed in analog form todigitizer board 1018 which converts the infrared images into digitalform and passes the digital image information to processor board 1022.The digital infrared images may be provided over a communication link170 through a gigabit ethernet board 1026 and/or to a display or othercomponents of infrared camera 100 through rear panel connections 1040.

Rotary cooler 1016 cools infrared sensor 1014. For example, in oneembodiment, rotary cooler 1016 is thermally coupled to infrared sensor1014. Fans 1036 may be provided to cool other portions of infraredcamera 100.

Infrared camera 100 also includes a Camera Link® connection 1038 forproviding an interface in accordance with the Camera Link® communicationprotocol. Infrared camera further includes a sensor board 1010 whichprovides filter identifier sensors 114 and filter wheel alignment sensor116 previously described herein. In addition, infrared camera includes astepper motor 1012 that rotates drive gear 124 as previously describedherein.

FIG. 13 illustrates a rear view of infrared camera 100 in accordancewith an embodiment of the invention. In particular, FIG. 13 showsvarious components on back cover 104 of infrared camera 100 which may beimplemented, for example, by additional circuitry 180 (shown in FIG. 2)and connected to main body 110 through communication link 170, CameraLink® connection 1038, and rear panel connections 1040 (shown in FIGS. 1and 10) where appropriate.

In this regard, back cover 104 includes communication link 170previously described herein, Camera Link® connection 1038 previouslydescribed herein, power switch 1032 previously described herein, and apower input port 1320 for receiving power from an external source (e.g.,received from power supply 1034 or a 24V power source). Back cover alsoincludes an analog video output port 1314 (e.g., for providing RBG videosignals in accordance with the SVGA standard to a display) and anS-Video port 1322 for providing S-Video signals to a display.

Back cover further includes an auxiliary port 1316 for providinginterfaces to measure external temperatures, communicate with externaloptical systems, send/receive transistor-transistor-logic (TTL) datawords, and other types of interfaces as may be desired for particularapplications.

In addition, back cover 104 includes a Universal Serial Bus (USB) hostconnection 1324 (e.g., for connecting a USB mass storage device) and aUSB client connection 1326 (e.g., for receiving appropriate command andcontrol communications). Back cover 104 also includes a plurality ofstatus lights 1312 (e.g., LEDs) for indicating the status of variousaspects of infrared camera 100 such as power status, FPA temperature,Inter-range instrumentation group (IRIG) timecode B lock, communicationconfiguration (e.g., USB or GigE Vision®), error status, or otheraspects of infrared camera 100.

Back cover 104 further includes a trigger input port 1328 for receivingTTL trigger signals to cause infrared camera 100 to generate a sequenceof frames, a synchronization input port 1330 for receiving TTLsynchronization signals to drive the frame rate of infrared camera 100,a composite video output port 1332 for providing National TelevisionSystem (NTCS) or Phase Alternating Line (PAL) video output signals to adisplay, a generator lock input port 1334 for receiving video signals tosynchronize video output signals of infrared camera 100, asynchronization output port 1336 for providing synchronization signalsto synchronize external cameras or instruments, and a timing input port1338 for receiving InterRange Instrumentation Group (IRIG) standardtiming input signals.

FIG. 11 illustrates a process of using filter wheel 120 in accordancewith an embodiment of the invention. In one embodiment, infrared camera100 may prompt a user to perform one or more of the steps of the processof FIG. 11 by, for example, displaying instructions to the user on adisplay, graphical user interface, or other appropriate user interfaceprovided by infrared camera 100.

In initial step 1105, filter identifiers 150 are installed on filterholders 130. In step 1110, filters 140 are installed in appropriatefilter holders 130 corresponding to the installed filter identifiers150. In step 1115, filter holders 130 having the installed filters 140and filter identifiers 150 are installed in filter wheel 120. Otherconfigurations of filter holders 130, filters 140, and filteridentifiers 150 may be used in other embodiments. As such, steps 1105 to1120 may be modified as appropriate to accommodate such configurationsand embodiments.

In step 1120, filter wheel 120 is installed in infrared camera 100. Inthis regard, shaft 129 of filter wheel 120 may be engaged with filterwheel gear 122 which engages with drive gear 124.

In step 1125, infrared camera 100 scans filters 140 currently installedin filter wheel 120 as further described in the process of FIG. 12. As aresult of step 1125, infrared camera 100 will have one or more records(for example, a populated table or other appropriate data structures) ofall filters 140 currently available to be used by infrared camera 100.

For example, in one embodiment, infrared camera 100 may maintain thefollowing Table 2 in memory 1024 of processor board 1020 to identifyfilters 140 currently installed in filter wheel 120:

TABLE 2 Filter Identifier 150 Filter Name/Target Filter Present 1 ND 1.0No 2 ND 2.0 No 3 ND 3.0 No 4 ND 0.3 No 5 ND 0.6 No 6 ND 1.45 No 7Standard MWIR No 8 ATM No 9 Solar Block (SRX) No 10 Thru Glass (TGL) No11 Glass High Temp (GHT) Yes 12 Narrow Band Flame or HT No 13 Broad BandFlame Yes 14 Polyethylene (PEN) No 15 Plastic No 16 CO2 Yes 17Nitrous-Oxide Yes 18 COS No

As shown in Table 2, four filters 140 corresponding to filteridentifiers 11, 13, 16, and 17 are currently installed in filter wheel120. As identified in Table 2 the installed filters 140 may be used whencapturing infrared images of high temperature glass, broad band flames,carbon dioxide, and nitrous oxide.

In step 1130, a target is selected for image capture. For example, inone embodiment, a user of infrared camera 100 may select the target bypositioning infrared camera 100 in proximity to the target. In anotherembodiment, the user may select the target using an appropriate userinterface of infrared camera 100 which identifies various types oftargets specified in Table 2 above. In another embodiment, processor1022 of infrared camera 100 may select the target for the user. Invarious embodiments, targets may correspond to objects, types ofmaterials, types of applications using infrared radiation (e.g., gasdetection including possibly type of gas, building diagnostics,utilities, surveillance, airborne, or other types of applications), orother subjects over any infrared wavelength ranges, over any temperatureranges, or having other characteristics as may be desired, as would beunderstood by one skilled in the art.

As previously described, different targets may radiate and/or absorbvarious infrared wavelengths depending, for example, on the materialcomposition of each target. Thus, different filters 140 may be requiredto capture infrared images of different targets. Accordingly, in step1135, an appropriate filter 140 is selected for capturing an infraredimage of the selected target.

In one embodiment, processor 1022 of infrared camera 100 may performstep 1135 by selecting an appropriate filter 140 based on the filteridentifier 150 associated with the selected type of target as identifiedby a lookup or reverse lookup performed on an appropriate table or otherdata structure stored in memory 1024. For example, if the selectedtarget corresponds to carbon dioxide, then processor 1022 may use Table2 described above to select the filter 140 corresponding to filteridentifier 17. In another embodiment, the user may perform step 1135 byselecting an appropriate filter 140 based on the type of target selectedin previous step 1130.

In step 1140, processor 1022 of infrared camera 100 determines whetherthe filter 140 selected in step 1135 is currently installed in filterwheel 120. For example, in one embodiment, processor 1022 may inspectTable 2 during step 1140. In this regard, if the “Filter Present” columnof Table 2 indicates that the selected filter 140 is currently installedin filter wheel 120, then the process of FIG. 11 continues to step 1150.Otherwise, the process of FIG. 11 continues to step 1145.

In step 1145, a condition exists in which the selected filter 140 to beused for capturing images of the selected target is not currentlyinstalled in filter wheel 120. This condition can be handled usingseveral different approaches as may be desired in different embodiments.

For example, in one embodiment, the process of FIG. 11 may return tostep 1110 in which the user installs the selected filter 140 in filterwheel 120. In this regard, a display of infrared camera 100 may informthe user of the particular filter 140 to be installed and remind theuser to rescan filters 140 (e.g., remind the user to repeat step 1125)after the particular filter 140 has been installed in filter wheel 120.Infrared camera 100 may also perform such a rescan operationautomatically in response to the installation of filter wheel 120 (e.g.,in response to step 1120 in which filter wheel 140 having the particularfilter is installed in infrared camera 100).

In another embodiment, processor 1022 of infrared camera 100 may selectanother filter 140 from the available filters 140 currently installed infilter wheel 120. For example, processor 1022 may determine which of thecurrently installed filters 140 best approximates the performance of thefilter 140 previously selected in step 1140 with the user optionallynotified by a display provided by infrared camera 100. Following theselection of another filter in step 1145, the process of FIG. 11 maycontinue to step 1150.

In yet another embodiment, the process of FIG. 11 may end (step 1170).In this regard, a display of infrared camera 100 may inform the user ofan error condition which can prevent images of the selected target frombeing captured.

Referring now to step 1150, infrared camera 100 positions the selectedfilter 140 (e.g., selected in step 1135 or step 1145) over aperture 112.For example, in one embodiment, stepper motor 1012 may rotate filterwheel 120 (e.g., by rotating drive gear 124) until the filter identifier150 corresponding to the selected filter 140 is positioned over filteridentifier sensors 114. The filter identifier 150 is read by filteridentifier sensors 114 and identified by infrared camera 100 ascorresponding to the selected filter 140. Then, the selected filter 140is rotated into position in front of aperture 112. For example, filterwheel 120 may be rotated approximately 180 degrees to move the selectedfilter 140 from a position in front of filter identifier sensors 114 toanother position in front of aperture 112. The position of filter wheel120 may be determined by filter wheel alignment sensor 116 readingposition identifiers 134.

In step 1155, processor 1022 configures appropriate camera settings(e.g., various selectable camera settings) of infrared camera 100 basedon the selected filter 140. For example, in one embodiment, processor1022 may adjust: integration time, gain, bandwidth, infrared detectorbiases, digital gain, digital offset, automatic or manual gain control,video contrast, and video brightness of infrared camera 100 as would beunderstood by one skilled in the art. As a result, infrared camera 100may be optimized to capture infrared images using the selected filter140.

In step 1160, infrared camera 100 captures one or more infrared imagesof the selected target using the selected filter 140 and appropriatelyconfigured settings of infrared camera 100. If infrared images ofadditional targets are desired (step 1165), then the process of FIG. 11returns to step 1130. Otherwise, the process of FIG. 11 ends (step1170).

FIG. 12 illustrates a process of scanning filter identifiers 150 inaccordance with an embodiment of the invention. As described above, theprocess of FIG. 12 may be performed during step 1125 of FIG. 11. In oneembodiment, infrared camera 100 may prompt a user to perform one or moreof the steps of the process of FIG. 12 by, for example, displayinginstructions to the user on a display or other appropriate userinterface provided by infrared camera 100.

In step 1210, a filter scan operation is triggered. For example, in oneembodiment, step 1210 may be performed by a user selecting anappropriate button on infrared camera 100. In this regard, it will beappreciated that labels 132 described above (see FIG. 2) may remind theuser to trigger the filter scan operation after one or more filters 140have been installed or replaced in filter wheel 120. In anotherembodiment, the filter scan operation may be triggered by infraredcamera 100 itself in response to the installation of filter wheel 120 instep 1120.

In step 1215, infrared camera 100 moves one of filters 140 currentlyinstalled in filter wheel 120 into position for reading its associatedfilter identifier 150. For example, in one embodiment, stepper motor1012 may rotate filter wheel 120 (e.g., by rotating drive gear 124)until the filter identifier 150 corresponding to the filter 140 ispositioned over filter identifier sensors 114.

In step 1220, filter identifier sensors 114 read the filter identifier150 associated with the filter 140. In step 1225, processor 1022 storesin memory 1024 a record of the filter 140 in response to the filteridentifier 150 read in step 1220. For example, in one embodiment,processor 1022 may populate a table such as Table 2 described above toindicate that the filter 140 having the filter identifier 150 read instep 1220 is currently installed in filter wheel 120.

If additional filters 140 currently installed in filter wheel 120 remainto be scanned (step 1230), then the process of FIG. 12 returns to step1215 where infrared camera 100 moves the next filter 140 into positionfor reading its associated filter identifier 150. If all filters 140 offilter wheel 120 have been scanned (step 1230), then the process of FIG.12 ends (step 1235).

Where applicable, various embodiments provided by the present disclosurecan be implemented using hardware, software, or combinations of hardwareand software. Also where applicable, the various hardware componentsand/or software components set forth herein can be combined intocomposite components comprising software, hardware, and/or both withoutdeparting from the spirit of the present disclosure. Where applicable,the various hardware components and/or software components set forthherein can be separated into sub-components comprising software,hardware, or both without departing from the spirit of the presentdisclosure. In addition, where applicable, it is contemplated thatsoftware components can be implemented as hardware components, andvice-versa.

Software in accordance with the present disclosure, such as program codeand/or data, can be stored on one or more machine readable mediums(e.g., computer readable media or other mediums). It is alsocontemplated that software identified herein can be implemented usingone or more general purpose or specific purpose computers and/orcomputer systems, networked and/or otherwise. Where applicable, theordering of various steps described herein can be changed, combined intocomposite steps, and/or separated into sub-steps to provide featuresdescribed herein.

Embodiments described above illustrate but do not limit the invention.It should also be understood that numerous modifications and variationsare possible in accordance with the principles of the present invention.Accordingly, the scope of the invention is defined only by the followingclaims.

1. An infrared camera comprising: an infrared sensor; a filter wheelcomprising: a plurality of filters adapted to selectively filterinfrared radiation prior to the infrared radiation being received by theinfrared sensor, and a plurality of filter identifiers associated withthe filters, wherein each filter identifier identifies a correspondingone of the filters; a plurality of sensors adapted to read the filteridentifiers to identify the filters installed in the filter wheel; amemory; and a processor adapted to store in the memory a record of thefilters installed in the filter wheel based on the filter identifiersread by the sensors.
 2. The infrared camera of claim 1, wherein theprocessor is adapted to determine whether a selected filter is installedin the filter wheel based on the record.
 3. The infrared camera of claim2, further comprising a motor adapted to rotate the filter wheel toposition the selected filter in front of the focal plane array inresponse to the processor if the selected filter is installed in thefilter wheel.
 4. The infrared camera of claim 2, wherein the processoris adapted to selectively configure settings of the infrared camerabased on the selected filter.
 5. The infrared camera of claim 1, whereinthe record associates the filters with the filter identifiers and aplurality of targets.
 6. The infrared camera of claim 5, wherein theprocessor is adapted to select one of the filters based on anassociation between the selected filter and a selected target identifiedin the record.
 7. The infrared camera of claim 1, wherein the filterwheel further comprises a plurality of filter holders adapted to securethe filters in the filter wheel, wherein the filter identifiers areprovided on the filter holders.
 8. The infrared camera of claim 1,wherein the filter identifiers are provided on the filters.
 9. Theinfrared camera of claim 1, wherein each filter identifier encodes abinary number to identify a corresponding one of the filters.
 10. Afilter wheel comprising: a plurality of filters adapted to selectivelyfilter infrared radiation corresponding to a plurality of targets; and aplurality of filter identifiers associated with the filters, whereineach filter identifier identifies a corresponding one of the filters,wherein the filter identifiers are adapted to be read by sensors of aninfrared camera.
 11. The filter wheel of claim 10, wherein the filterwheel further comprises a plurality of filter holders adapted to securethe filters in the filter wheel, wherein the filter identifiers areprovided on the filter holders.
 12. The filter wheel of claim 10,wherein the filter identifiers are provided on the filters.
 13. Thefilter wheel of claim 10, wherein each filter identifier encodes abinary number to identify a corresponding one of the filters.
 14. Thefilter wheel of claim 10, wherein the filter wheel is adapted to berotated by an infrared camera to selectively position the filters infront of an infrared sensor of the infrared camera.
 15. A method ofidentifying filters of an infrared camera, the method comprising:scanning a plurality of filter identifiers associated with the filtersinstalled in a filter wheel of the infrared camera, wherein the filtersare adapted to selectively filter infrared radiation prior to theinfrared radiation being received by an infrared sensor of the infraredcamera; determining whether a selected filter is installed in the filterwheel based on the scanning; and rotating the filter wheel to positionthe selected filter in front of an infrared sensor of the infraredcamera if the selected filter is installed in the filter wheel.
 16. Themethod of claim 15, wherein the scanning comprises: reading the filteridentifiers using sensors of the infrared camera; and storing a recordof the filters installed in the filter wheel based on the filteridentifiers read by the sensors.
 17. The method of claim 15, wherein thescanning is triggered by a user of the infrared camera.
 18. The methodof claim 15, wherein the scanning is triggered by the infrared camera.19. The method of claim 15, further comprising: prompting a user of theinfrared camera to install the selected filter in the filter wheel ifthe selected filter is not installed in the filter wheel; and scanning afilter identifier associated with the selected filter.
 20. The method ofclaim 15, further comprising selectively configuring settings of theinfrared camera based on the selected filter.
 21. The method of claim15, further comprising associating the filters with the filteridentifiers and a plurality of targets.
 22. The method of claim 21,further comprising selecting the selected filter based on an associationbetween the selected filter and a selected one of the targets.
 23. Themethod of claim 15, wherein the filter wheel further comprises aplurality of filter holders adapted to secure the filters in the filterwheel, wherein the filter identifiers are provided on the filterholders.
 24. The method of claim 15, wherein the filter identifiers areprovided on the filters.
 25. The method of claim 15, wherein each filteridentifier encodes a binary number to identify a corresponding one ofthe filters.
 26. An infrared camera comprising: a plurality of filtersadapted to selectively filter infrared radiation prior to the infraredradiation being received by an infrared sensor for the infrared camera;means for securing the filters; means for identifying each of thefilters; means for reading the identifying means to identify the filtersinstalled in the securing means; and means for storing a record of thefilters installed in the securing means based on the identifying meansread by the reading means.